Voltage-controlled oscillators (“VCOs”) are used in a variety of integrated circuit applications. A critical performance parameter of a VCO is the frequency of its output signal. Some integrated circuit applications may require the oscillator frequency to be adjustable. For example, tuning of a VCO output frequency may be required to account for frequency variation that may occur across a range of potential operating conditions, including, but not limited to, varying temperature, varying supply voltage, or semiconductor process variation. Further, some integrated circuit applications may require multiple oscillator frequencies. In multi-mode or multi-band cellular phone transceiver designs, for example, the transceiver may need to operate at different frequencies at different times depending on the mode in which the transceiver is operating.